It is know that most of the currently known anchor devices comprise an expansion bolt and a fastening screw adapted to be inserted and screwed into the bolt to determine the expansion of the same inside the wall. Specifically, the bolt typically consists of a deformable tubular element formed by plastic or metallic material, which is adapted to be inserted in a hole obtained in a wall, in a body or in an anchor element, with its longitudinal axis coaxial to the axis of the hole itself.
In the above-mentioned expansion bolts, the tubular element normally consists of a deformable central shank, of a head connected to a first end of the central shank, and of a cylindrical collar, which is connected to a second end of the central shank and is provided with an annular abutment flange.
Unfortunately, the structure of the above-described expansion bolts is such to allow an effective anchoring only on given types of wall, i.e. for a specific application, but is inadequate when the bolt must be used for anchoring onto walls having structural features different from those contemplated for the application the expansion bolt has been designed for.
Specifically, the expansion bolts of the above-mentioned anchor devices are not capable of ensuring an effective fastening, i.e. do not present an adequate operation to be used in all the following applications: anchoring on walls made with bricks provided with reciprocally distanced internal webs delimiting voids or spaces filled with low-consistency material; and/or anchoring on walls made with a relatively friable or heterogeneous material, such as for example plywood walls, walls made of coarse, not very compact concrete; and/or anchoring on walls made of compact materials i.e. having a high consistency, such as for example concrete walls or natural stone walls or walls made of solid bricks, i.e. filled with high consistency material.